TWI401724B - Apparatus for sub-zero temperature ion implantation - Google Patents

Abstract

An ion implanter that comprises a chuck assembly having a chuck to clamp, hold, and cool a wafer is disclosed. The chuck is cooled by a cooling assembly circulated with a special coolant, such that the chuck can be maintained at very low temperatures. A mechanical design is provided to minimize the direct surface-to-surface contact area between the chuck and a base, which is employed to support the chuck. The mechanical design includes fasteners for providing mechanical support between the chuck and the base and thermal insulators for providing thermal insulation between the chuck and the base.

Description

Device capable of performing low temperature ion implantation

The present invention relates to an ion implanter operating at a temperature below zero Celsius, and in particular to an ion implanter that can effectively isolate heat generated in other portions of the ion implanter from being transferred to the wafer and the carrier.

A typical ion implanter includes an ion source disposed in an ion source chamber, the ion chamber being coupled to a voltage source to conduct ions, and thereby projecting an ion beam to a mass analyzer (mass analyzer) having an analyzer magnet. The mass analyzer controls the composition and orientation of the ion beam and projects the ion beam through a plasma shower to electrically neutralize the ion beam. The ion beam is ultimately projected onto a wafer so that the wafer can be scanned by the ion beam.

Maintaining the ion-implanted wafer at a low temperature during the ion implantation process for fabricating a semiconductor device can reduce implant damage, avoid self-annealing effects, and the like. In addition, semiconductor devices implanted with ions at low temperatures have low leakage current, low parasitic capacitance, and low parasitic resistance, so that high-reliability and high-fidelity signal output can still be achieved after long-term high-temperature operation.

Typically, ion implanters utilize a chuck to hold the wafer to be implanted. In order to control the wafer in a low temperature environment, the carrier is connected to a water-cooling assembly, and a cooling gas can be applied to the back of the wafer to assist in heat dissipation. The first figure shows a block diagram of a conventional technique for cooling a carrier 10 located in an ion implanter with a water cooling assembly 2. Among them, the water-cooling assembly 2 uses distilled water or deionized water (DI) as a circulating refrigerant. A pump 4 is used to deliver distilled or deionized water from a storage tank 6 to a supply tank 8 and then to a carrier 10 via a control valve 12. A flow sensor 14 is used to measure the flow of water delivered to the carrier 10. A temperature meter 16 measures the temperature of the water in the reservoir 6. A pressure gauge 18 measures the pressure in the supply tank. In addition, a heat exchanger 19 is used to reduce the water temperature of the distilled water or the deionized water, and the heat exchanger 19 introduces cold water or other refrigerant from the common input to reduce the water temperature of the distilled water or the deionized water, the warm water after the heat exchange or Other refrigerants are sent away via the common output.

Recently, as the line width of semiconductor processes has become smaller and smaller, the application of ultra shallow junctions has become more frequent, and the demand for ion implantation at sub-zero temperatures has increased. In the case of extreme temperature requirements, an exhaustive thermal analysis is required to confirm any heat source and its path that may cause heat to be raised to the wafer.

The second figure shows a standard electro-static chuck assembly 26 of the prior art, which includes a carrier 20 that can be used to fix and cool a wafer for ion implantation (not shown). Show). The carrier 20 is secured to the surface of a base 22 (which may be considered part of the ion implanter) by a plurality of screws 24. The base 22 provides mechanical support for the carrier 20 and also provides an accommodation space for the cooling circuit to be connected to the circuit.

During ion implantation, the ion beam is absorbed by the upper surface of the wafer causing the wafer temperature to rise. In order to keep the temperature of the wafer within an acceptable range, the heat generated during the ion implantation process must be transferred from the wafer to the refrigerant in the carrier (which can also be transferred to the back of the wafer). Wafer cooling gas). This heat transfer path includes: (1) passing through the wafer; (2) passing through the interface of the wafer and the carrier 20; and (3) passing through the portion of the carrier 20 to the cold water line in the carrier 20.

Among them, the maximum heat transfer impedance of the above heat transfer path is usually the interface between the wafer and the carrier, which is also the reason why the cooling gas is applied to the back surface of the wafer. In addition, although the cooling water can carry away most of the heat, there is still a small portion of the heat left in the base 22, even through the base 22 to other components of the ion implanter. Since the slight temperature increase of the base does not substantially cause too much trouble, the prior art does not take any means to thermally isolate the base 22 from the carrier 20.

However, conventional ion implanters will encounter difficulties when ion implantation requires operation at temperatures below zero degrees Celsius C or below. First, the refrigerant used in the prior art, such as distilled or deionized water, will solidify under atmospheric pressure, in other words, it will not operate at zero degrees C Celsius. Moreover, since the prior art does not take any means to thermally isolate the base 22 from the carrier 20, the heat of the base 22 can be transferred to the wafer via the carrier 20, resulting in an increase in wafer temperature.

Therefore, there is a need to provide a new ion implanter that can operate at zero degrees C Celsius to improve the lack of conventional techniques.

Embodiments of the present invention provide a device that operates below zero degrees Celsius C, particularly a carrier assembly or an ion implanter, to overcome the deficiencies of the prior art.

An embodiment of the present invention provides a carrier assembly including a carrier for holding a wafer, a base connectable to a portion of an ion implanter, and at least one fixed A fastener secures the carrier to the base, whereby there is no direct physical contact between the carrier and the base, but only indirect physical contact through the fastener.

An embodiment of the invention provides an ion implanter comprising an ion beam generating assembly to generate an ion beam and a carrier assembly. The carrier assembly includes a carrier for holding a wafer for ion implantation, a base connected to a portion of the ion implanter, and at least one fixing member for fixing the carrier to the base such that the carrier and the base There is absolutely no direct physical contact between them.

2‧‧‧Water cooling assembly

4‧‧‧ pump

6‧‧‧ storage tank

8‧‧‧ supply slot

10‧‧‧Hosting

12‧‧‧Control valve

14‧‧‧Flow sensor

16‧‧‧temperature instrument

18‧‧‧ Pressure gauge

19‧‧‧ heat exchanger

20‧‧‧Hosting

22‧‧‧Base

24‧‧‧ screws

26‧‧‧Carriage assembly

30‧‧‧Carriage assembly

32‧‧‧Hosting

34‧‧‧Base

36‧‧‧Fixed parts

42‧‧‧Hosting

44‧‧‧Base

46‧‧‧Fixed parts

48‧‧‧ Thermal insulation

49‧‧‧ gap

53‧‧‧First thermal insulation

55‧‧‧Second thermal insulation

57‧‧‧The third thermal insulation

59‧‧‧Four thermal insulation

90‧‧‧Reaction room

92‧‧‧Seat

94‧‧‧Cooling assembly

The first figure shows a block diagram of a conventional technique for cooling a carrier with a water-cooled assembly; the second figure shows a standard electrostatic carrier assembly according to the prior art; and the third figure shows a load according to an embodiment of the invention. a side view of the seat assembly; a fourth view showing a fixing member according to an embodiment of the present invention; and a fifth drawing showing a fixing member according to an embodiment of the present invention, and having a first thermal insulating member between the fixing member and the base; 6 shows a fixing member according to an embodiment of the present invention, and a second thermal insulating member is disposed between the fixing member and the carrier; the seventh figure shows a fixing member according to an embodiment of the present invention, and the fixing member is covered with a first member. a three-hot insulation member; the eighth diagram shows a fixing member according to an embodiment of the present invention, and the fixing member is covered with a fourth thermal insulation member by air; and the ninth diagram shows an ion implanter according to an embodiment of the present invention. Block diagram.

Various modifications, changes and permutations of the preferred embodiments of the invention, as well as the principles and features of the invention described herein are readily apparent to those skilled in the art. Therefore, the scope of the invention is not limited by the embodiment, but the broadest scope of the invention is in accordance with the concepts and features disclosed herein. In the description of the specification, numerous specific details are set forth in the description of the invention. In addition, well-known steps or elements are not described in detail to avoid unnecessarily limiting the invention.

The present invention discloses an ion implanter comprising an ion beam generating assembly to produce an ion beam, and a carrier assembly for immobilizing and cooling a wafer for ion implantation. According to various embodiments of the present invention, the constituent elements of the ion beam generating assembly are not limited, and any known or commercial product may be used as an element thereof. For example, the ion beam generating assembly may include an ion source, a lead electrode, and a Analyze the magnet. Here, the illustration and related description are omitted.

One of the features of the present invention is to change the mechanical structure between the carrier and the base to improve the lack of prior art. Here, the carrier and the base are not greatly changed in structure, and the conventional carrier and base design can also be adopted in the embodiment of the present invention. The changes made in embodiments of the invention focus on minimizing the direct physical contact area between the carrier and the pedestal. In other words, embodiments of the present invention focus on the interface design between the carrier and the base.

The third figure shows a carrier assembly 30 in accordance with an embodiment of the present invention in which the carrier 32 and the base 34 are secured by at least one fastener 36. Obviously, there is no direct physical contact between the carrier 32 and the base 34, but an indirect entity through the at least one fixing member 36. The contact is such that the area of overlap of the carrier 32 with the base 34 is greater than (or even significantly greater than) the direct physical contact area between the carrier 32 and the fixture 36. Thus, the fixture 36 is the only thermal conduction path between the carrier 32 and the base 34 such that heat transfer between the carrier 32 and the base 34 can be effectively reduced. Here, the base 34 is used to support the carrier 32 and is connected to a portion of an ion implanter. In addition, in one embodiment, the carrier 32 can include a bottom layer, an intermediate layer, and an upper layer. The bottom layer provides a mechanical and electrical connection interface with the base 34. The middle layer is distributed with a refrigerant line and a wafer cooling gas line for separate transmission. The upper layer is used to set the circuit and the gas refrigerant is introduced into the carrier refrigerant and the wafer cooling gas for the back surface of the wafer.

In particular, when the heat transfer transmitted through the fixing member 36 is greatly reduced, the heat transfer efficiency can be further improved. Therefore, in an embodiment of the present invention, as shown in the fourth figure, the material of the fixing member 46 may include metal or other materials and is covered by a thermal insulating member 48. In addition, the thermal insulator 48 may not be in close proximity to the fixture 46, and the thermal insulator 48 may also have the function of supporting the carrier 42. Because both the fixture 46 and the thermal insulator 48 have a small surface area, the structure provided by embodiments of the present invention can significantly reduce the physical contact area of the carrier 42 with the base 44. It should be noted that the structure of the embodiment of the present invention still has a gap 49 between the carrier 42 and the base 44, so that the fixing member 46 becomes the only heat conduction path between the carrier 42 and the base 44. Here, since the efficiency of heat conduction is much higher than the efficiency of thermal convection and heat radiation, the gap 49 greatly reduces the heat propagation path between the carrier 42 and the base 44, so that the heat is fixed. The piece 46 becomes the only effective heat transfer path between the carrier 42 and the base 44. In an embodiment of the invention, a plurality of fixing members 46 are disposed at equal intervals on the edge of the base 44. In another embodiment of the invention, 12 small thermal insulating members 46 are made of Torlon® or PEEK. They are disposed at equal intervals on the edge of the base 44. However, the concept of the present invention does not limit the distribution of the fixture 46 and the thermal insulator 48.

How to provide good thermal insulation of the carrier 42 from the base 44 can be accomplished in several ways. The fifth figure shows a fixing member 46 according to an embodiment of the present invention, and a first thermal insulating member 53 is disposed between the fixing member 46 and the base 44. The sixth figure shows a fixing member 46 according to an embodiment of the present invention, and a second thermal insulating member 55 is disposed between the fixing member 46 and the carrier 44. The seventh figure shows a fixing member 46 according to an embodiment of the present invention. A third thermal insulating member 57 is disposed between the carrier 42 and the base 44 and at least partially directly covers the fixing member 46. The eighth figure shows a fixing member 46 according to an embodiment of the present invention. A fourth thermal insulating member 59 is disposed between the carrier 42 and the base 44, and indirectly (spaces) covers the fixing member 46.

In addition to the fasteners described above, the physical contact between the carrier and the base is only the refrigerant line and the wafer cooling gas line. Accordingly, in one embodiment of the invention, the refrigerant line and/or the wafer cooling gas line are sealed with at least one O-ring. Therefore, the physical contact with the carrier is transmitted only through the small-area fixing member, the insulating member and the O-ring, so that the heat conduction between the carrier and the base becomes small. In addition, since the effects of thermal radiation and thermal convection are relatively small, heat exchange between the carrier via thermal radiation or thermal convection and the base or other surrounding components can be ignored.

In addition to the practices provided above, the present invention provides yet another practice. The ninth diagram shows a block diagram of an ion implanter in accordance with an embodiment of the present invention, comprising a carrier 92 located in a chamber 90 and a cooling assembly 94 for cooling the carrier 92, wherein the cooling assembly 94 It is an improvement of the traditional water cooling assembly 2. Here, the cooling assembly 94 of the present invention uses a special refrigerant, which is located in the refrigerant line, is pumped to the carrier 92 to absorb heat, and then the special refrigerant whose temperature rises is then sent to the heat of the cooling assembly 94. The exchanger exchanges heat with a coolant of a freezing unit (which can be the same as a special refrigerant) so that it is at a temperature drop. Here, the freezing unit may be located outside the ion implanter. Here, the difference between the special refrigerant and the conventional water as the refrigerant is that the special refrigerant can be operated below zero degrees C and atmospheric pressure without solidification. Further, the freezing unit of the cooling assembly 94 of the present invention must have an operable temperature range of not more than zero degrees Celsius C and the ability to transport the special refrigerant. Of course, all O-rings, pipelines, inductors, meters, valves, etc. must have specifications that are compatible with the specifications of the particular refrigerant. Here, the special refrigerant must have low viscosity, high density, high thermal conductivity, and high specific heat characteristics below zero degrees C. Here, a secondary consideration in selecting this particular refrigerant is its safety, compatibility, and compatibility with current semiconductor production. For example, Fluorinert® FC-3283 fluid produced by 3M Company can be selected as the special refrigerant. For example, the SMC HRZ001-L-Z Thermo chiller, manufactured by SMC Pneumatics, Inc., Indianapolis, USA, has an operating temperature range and refrigeration capacity that meets the requirements and can be selected as the special refrigeration unit.

In addition, the design of the cooling assembly of the embodiment of the present invention must match the characteristics of the particular refrigerant that is still operable when it is below zero degrees C. For example, all tubes, especially flexible tubes, can be modified to have high chemical compatibility, can be packaged using standard fittings, and have good performance over a predetermined operating temperature range. Extensibility. For example, all fittings may use a compression forming element having a ferrule, a barb, or the like. Additionally, in an embodiment of the invention, all of the lines and fittings are covered with an insulating layer to avoid condensation on the outer surface thereof. Herein, in an embodiment of the invention, in a region that is not covered by the insulating layer, it is necessary to surround and purge with a dry cleaning gas to avoid condensation. The common dry cleaning gas may be dry nitrogen or Other gases with very low dew points. In an embodiment of the invention, all of the O-rings are made of ethylene propylene diene rubber (Ethylene Propylene Diene). The Monomer (EPDM), flow sensor uses a Proteous® flow sensor to be compatible with special refrigerants (Fluorinert FC-3283) and has an operating temperature range that can operate below zero degrees C. In addition, in an embodiment of the present invention, the remaining features of the cooling assembly 94 may be the same as the SMC HRZ001-L-Z Thermo chille of the water cooling assembly 2 as described above, and the technical content thereof will not be described again.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the claims of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

42‧‧‧Hosting

44‧‧‧Base

46‧‧‧Fixed parts

48‧‧‧ Thermal insulation

49‧‧‧ gap

Claims (10)

An ion implanter comprising: an ion beam generating assembly for generating an ion beam; and a carrier assembly comprising: a carrier for fixing a wafer implanted by the ion beam a base connected to a portion of an ion implanter: at least one fixing member for fixing the carrier on the base such that there is no direct physical contact between the carrier and the base; and a cooling assembly The cooling assembly delivers a special refrigerant to the carrier such that the special refrigerant rises in temperature due to absorption of the heat of the carrier, and delivers the special refrigerant to a heat exchanger of the cooling assembly to be frozen The heat exchange of a coolant of the unit causes the temperature of the special refrigerant to decrease, and the special refrigerant has the characteristics of low viscosity, high density, high thermal conductivity, and high specific heat under a predetermined operating temperature range. An ion implanter as claimed in claim 1, wherein the cooling assembly has a high chemical compatibility, can be packaged using a standard fitting, and has good ductility over a predetermined operating temperature range, where the fitting A press-formed member having a ferrule and a barb or the like can be used. An ion implanter according to claim 2, wherein the portion not covered by an insulating layer and the portion are surrounded and cleaned by a dry cleaning gas, the cooling assembly using a plurality of phases Retaining the special refrigerant and having at least one O-ring that can operate at a temperature range below zero degrees C. The ion implanter of claim 1, wherein the fixing members are disposed on the base at equal intervals. The ion implanter of claim 1, wherein the physical contact area between the fixing member and the carrier is much smaller than the overlapping area between the carrier and the base. An ion implanter according to claim 1, wherein a first thermal insulating member is disposed between the fixing member and the base. An ion implanter according to claim 1, wherein a second thermal insulating member is disposed between the fixing member and the carrier. The ion implanter of claim 1, wherein a third thermal insulator is disposed between the carrier and the base. The ion implanter of claim 8 wherein the physical contact area between the third thermal insulator and the carrier is much smaller than the overlap area between the carrier and the base. The ion implanter of claim 1, wherein the carrier has a bottom layer, a middle layer and an upper layer, the bottom layer providing a mechanical and electrical connection interface with the base, the middle layer is distributed with a refrigerant pipeline and a crystal A circular cooling gas line is used to separately transport refrigerant for the carrier and wafer cooling gas for the backside of the wafer, the upper layer for setting up the circuit and introducing the wafer cooling gas.